/*
 * Generic Event Loop
 *
 * Copyright (C) 2014-2016 Ideas on board Oy
 *
 * Contact: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

#define _DEFAULT_SOURCE
#include <errno.h>
#include <poll.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <sys/select.h>

#include <xlnx-events.h>
#include <xlnx-list.h>
#include <xlnx-tools.h>

#include "xlnx-priv.h"

#define SELECT_TIMEOUT		2000		/* in milliseconds */

struct xlnx_events {
	struct list_entry events;
	bool done;

	int maxfd;
	fd_set rfds;
	fd_set wfds;
	fd_set efds;
};

struct xlnx_event_fd {
	struct list_entry list;

	int fd;
	int type;
	void (*callback)(void *priv);
	void *priv;
};

static void xlnx_events_watch_fd(void *handler, int fd, int event_type,
				 void(*callback)(void *), void *priv)
{
	struct xlnx_events *events = handler;
	struct xlnx_event_fd *event;

	event = malloc(sizeof *event);
	if (event == NULL)
		return;

	event->fd = fd;
	event->type = event_type;
	event->callback = callback;
	event->priv = priv;

	switch (event->type) {
	case POLLIN:
		FD_SET(fd, &events->rfds);
		break;
	case POLLOUT:
		FD_SET(fd, &events->wfds);
		break;
	case POLLERR:
		FD_SET(fd, &events->efds);
		break;
	}

	events->maxfd = max(events->maxfd, fd);

	list_append(&event->list, &events->events);
}

static void xlnx_events_unwatch_fd(void *handler, int fd)
{
	struct xlnx_events *events = handler;
	struct xlnx_event_fd *event = NULL;
	struct xlnx_event_fd *entry;
	int maxfd = 0;

	list_for_each_entry(entry, &events->events, list) {
		if (entry->fd == fd)
			event = entry;
		else
			maxfd = max(maxfd, entry->fd);
	}

	if (event == NULL)
		return;

	switch (event->type) {
	case POLLIN:
		FD_CLR(fd, &events->rfds);
		break;
	case POLLOUT:
		FD_CLR(fd, &events->wfds);
		break;
	case POLLERR:
		FD_CLR(fd, &events->efds);
		break;
	}

	events->maxfd = maxfd;

	list_remove(&event->list);
	free(event);
}

static void xlnx_events_dispatch(struct xlnx_events *events, const fd_set *rfds,
				 const fd_set *wfds, const fd_set *efds)
{
	struct xlnx_event_fd *event;
	struct xlnx_event_fd *next;

	list_for_each_entry_safe(event, next, &events->events, list) {
		if (event->type == POLLIN && FD_ISSET(event->fd, rfds))
			event->callback(event->priv);
		else if (event->type == POLLOUT && FD_ISSET(event->fd, wfds))
			event->callback(event->priv);
		else if (event->type == POLLERR && FD_ISSET(event->fd, efds))
			event->callback(event->priv);

		/* If the callback stopped events processing, we're done. */
		if (events->done)
			break;
	}
}

/**
 * \brief Start and run the event loop
 * \param xv the library context
 *
 * This function starts and runs the event loop synchronously, waiting for
 * events and dispatching them as they arrive. It doesn't return until the loop
 * is requested to stop by a call to xlnx_events_stop() or a fatal error occurs.
 *
 * \return false if the loop exited due to a stop request, or true if it exited
 * due to a fatal error.
 */
bool xlnx_events_loop(struct xlnx_video *xv)
{
	struct xlnx_events *events = xlnx_video_get_event_handler_data(xv);

	events->done = false;

	while (!events->done) {
		struct timeval timeout;
		fd_set rfds;
		fd_set wfds;
		fd_set efds;
		int ret;

		timeout.tv_sec = SELECT_TIMEOUT / 1000;
		timeout.tv_usec = (SELECT_TIMEOUT % 1000) * 1000;
		rfds = events->rfds;
		wfds = events->wfds;
		efds = events->efds;

		ret = select(events->maxfd + 1, &rfds, &wfds, &efds, &timeout);
		if (ret < 0) {
			/* EINTR means that a signal has been received, continue
			 * to the next iteration in that case.
			 */
			if (errno == EINTR)
				continue;

			printf("error: select failed with %d\n", errno);
			break;
		}
		if (ret == 0) {
			/* select() should never time out as the library is
			 * supposed to process images continuously. A timeout is
			 * thus considered as a fatal error.
			 */
			printf("error: select timeout\n");
			break;
		}

		xlnx_events_dispatch(events, &rfds, &wfds, &efds);
	}

	return !events->done;
}

/**
 * \brief Stop the event loop
 * \param xv the library context
 *
 * Stop the running event loop started with xlnx_events_loop(). The loop is
 * stopped asynchronously after processing the next event. This function doesn't
 * wait for the loop to exit before returning.
 */
void xlnx_events_stop(struct xlnx_video *xv)
{
	struct xlnx_events *events = xlnx_video_get_event_handler_data(xv);

	events->done = true;
}

static const struct xlnx_video_event_operations xlnx_events_ops = {
	.watch = xlnx_events_watch_fd,
	.unwatch = xlnx_events_unwatch_fd,
};

/**
 * \brief Initialize event handling
 * \param xv the library context
 *
 * This function registers event handling operations with the library context
 * \a xv. The event handling implementation is based on a select() loop that is
 * controlled through the xlnx_events_loop() and xlnx_events_stop() functions.
 *
 * Before destroying the library context event handling must be cleaned up with
 * a call to xlnx_events_fini().
 *
 * \return 0 on success or a negative error code on failure.
 */
int xlnx_events_init(struct xlnx_video *xv)
{
	struct xlnx_events *events;

	events = calloc(1, sizeof(*events));
	if (!events)
		return -ENOMEM;

	FD_ZERO(&events->rfds);
	FD_ZERO(&events->wfds);
	FD_ZERO(&events->efds);
	events->maxfd = 0;
	list_init(&events->events);

	xlnx_video_set_event_handler(xv, &xlnx_events_ops, events);
	return 0;
}

/**
 * \brief Clean up event handling
 * \param xv the library context
 *
 * This function cleans up event handling. It must be called before destroying
 * any library context previously initialized by a call to xlnx_events_init().
 */
void xlnx_events_fini(struct xlnx_video *xv)
{
	struct xlnx_events *events = xlnx_video_get_event_handler_data(xv);

	if (events) {
		xlnx_video_set_event_handler(xv, NULL, NULL);
		free(events);
	}
}